Whether you split expenses down the middle or make the costlier bills the better-paid person's problem, you can't cohabit without knowing how you're funding your lifestyle. So figure it out well before you sign the lease or mortgage. While you can determine how much beer you'll keep in your fridge after you move in, your basic finance strategy can't really wait.

2. Air conditioning, or at least a kick-ass fan

Extreme heat can make anyone cranky. High temps when you're sharing a bed with someone can spell sleepless nights. No matter you budget, your ability to rest or just hang out sans sweat midday isn't worth sacrificing. So splurge on an A/C unit or a powerful fan that actually cools a small room.

3. A bigger-than-twin-size bed

Despite the never-before-experienced aches you got from sharing those skinny college-dorm beds, no one regrets having snuggled up on a narrow mattress, even if a roommate was mere feet away. You will regret continuing the tradition post-graduation. Something about having a degree — or rather, not living in a dorm — makes you crave certain luxuries, like enough room to sleep comfortably. If you can't afford or fit a queen-size bed in your shared pad, spring for a full-size mattress, so you're less likely to bruise each other mid-slumber — and hate your space-cramping bedfellow each morning.

4. Patience, especially if there's only one bathroom

Love goes a long way in making living together work. It's not all that matters when you have to use the facilities and your partner-in-sin is doing God-knows-what in the loo. In those cases, it's easy to lose your sh*t, both figuratively and literally. But you can't because this scenario will happen over and over. It'll also occur when you're waiting to pour milk on your cereal, read the occasional piece of mail addressed to both of you, and use the lone full-length mirror. And sometimes, you'll be the one engaging in slow, torturous hair removal behind the closed door when your roomie needs to get in. Taking one's time occasionally doesn't warrant a fight.

5. Clear, mutually agreed upon rules about visitors

You don't need a Big Bang Theory-esque roommate contract, but you should shake hands on some guidelines about who can (and can't) come over and how much notice (if any) you need. That's because it stinks to come home from work to your potential in-laws sprawled out on your couch and have your quiet, Netflix-watching-evening dreams shattered by your significant other's rowdiest pals.

6. Out-of-home communication skills

It's easy to take for granted that you'll see your beloved at some point most days. Still, cohabitors owe each other info on their whereabouts, moreso if you usually eat dinner together and you're considering attending a post-work happy hour. No matter how busy your workday or crappy your cell service, it's only fair to let your roomie know what you're doing and more importantly, when you'll be home. Waiting up isn't fun for anyone.